Sony Ericsson has released two major updates for the Xperia X2 in the last couple of months. The new MR2 software update brings the Windows Mobile 6.5.3 update to the Xperia X2. Here is more info on the newest software update:

The new software update brings more performance and stability improvements throughout the X2. This release contains WM6.5.3 (Maldives) with much improved finger friendliness, a consistent touchable UI, more improvements to core Sony Ericsson and Microsoft applications and enhanced speed/performance throughout the device.